In single-phase modulation of PWM inverters, the pulse width is 120°. For an input voltage of 220 V dc, the rms value of output voltage is

To calculate the RMS (root mean square) value of the output voltage in a single-phase PWM inverter, the formula for the output voltage can be derived from the modulation technique.

Given:

– DC input voltage (V_dc) = 220 V

– Pulse width (θ) = 120°

The RMS output voltage (V_rms) for a PWM inverter can be calculated using the formula:

[ V_{rms} = V_{dc} cdot frac{1}{pi} cdot int_{0}^{theta} sin(theta) , dtheta ]

For a pulse width of 120°, which is ( frac{120}{360} ) or ( frac{1}{3} ) of the full cycle:

1. The integral ( int_{0}^{theta} sin(theta) , dtheta ) for 120° can be simplified, and it’s also dependent on the specific PWM method being used (considering the modulation index).

2. The average output voltage can be approximated as ( frac{2 cdot V_{dc}}{pi} cdot text{Duty Cycle} ), where the duty cycle here is ( frac{theta}{360} = frac{120}{360} = frac{1}{3} ).

Using a detailed PWM converter formula, we would get:

[

V_{rms} =